This proposal seeks to establish a Clinical Research Center for Periodontal Disease at Virginia Commonwealth University. The Center will provide a focus at VCU for investigative effort related to periodontal disease. Projects proposed in this application are divided into three main sections: 1. Microbiological Investigations; 2. Immunological Investigations; 3. PMN Functions. Objectives and methods for each section are as follows: 1. The bacteria present at the advancing front of disease in gingivitis, moderate periodontitis, severe periodontitis, juvenile periodontitis, minimal periodontitis in older individuals, and in ANUG will be identified. Anaerobic sampling and isolation procedures, direct microscopic counts, culturing, and identification will be carried out following practices used previously at VPI Anaerobe Lab for similar characterizations of gut flora. Flora will also be characterized before and after two forms of therapy of periodontitis to assess changes associated with transitions between health and disease. 2. Ongoing study of the immunology of severe periodontitis will be broadened by beginning antigen purifications, determining class specific antibody proportions in serum, testing cryopreservative methods for lymphocytes, measuring immunoglobulin and complement components in serum and gingival fluid, assaying complement activation by oral bacteria, and attempting to detect antigens and antibodies in periodontally diseased tissue. Antigen purification will be approached by standard preparative methods to yield bacterial cell wall material, membrane material, protoplasmic material, and subfractions thereof. Reactivity with antigens will be assessed by radioimmunoassay for antibody and by peripheral lymphocyte blastogenesis. Other methods used in this section include radial immunodiffusion, laser nephelometry, and immunofluorescence microscopy. 3. Chemotaxis and phagocytosis by PMN in severe periodontitis and juvenile periodontitis will be assayed to confirm PMN defects in these populations; the basis for defects will be sought by assays of receptor recognition, cyclic nucleotide metabolism, calcium flux and microtubule assembly. Appropriate methods will be used. Also in this section, an attempt to detect chemotactic peptides associated with oral bacteria will be made, using a specific binding assay inhibition with a radiolabeled synthetic peptide chemoattractant. An (Text Truncated -Exceeds Capacity)